Apparatus for drying vegetable fiber such as bagasse and the like



Oct. 25, 1938. G, J, UPSCOMB 2,134,229

APPARATUS FOR DRYING VEGETABLE FIBER SUCH AS BAGASSE AND THE LIKE FiledOct. 20, 1934 [via MW Patented Oct. 25, 1938 UNITED STATES PATENT OFFICEAPPARATUS FOR DRYING,VEGETABLE FI- BER- SUCH AS BAGASSE AND THE LIKEGaston J. Lipscomb, Montclair, N. J. Application October 20, 1934,Serial No. 749,258

1 Claim.

The present invention relates to the apparatus for drying vegetablefiber such as bagasse, and aims generally to improve existing methodsand apparatus for that purpose.

More particularly, the present invention aims to improve the method andapparatus for drying vegetable fiber as is disclosed in my copendingapplication Serial No. 738,112, filed August 2, 1934, by providing a newmethod and apparatus which will substantially dry bagasse to a drynessof approximately 7% in a minimum of time and under materially reducedfire hazards.

One of the principal aims and objects of the invention is to provide animproved method and apparatus for drying ,bagasse which will give As inthe case of my prior application Serial No. 738,112, above referred to,the wet bagasse containing from to .of moisture, is delivered to a driercasing through which hot air is circulated, the bagasse being fed tosuccessive tiers during its progress through the drier casing. Accordingto the present invention, the wet bagasse is delivered to a feeding box,I 0, which may be a circular sheet mounted above the drier casing I3.Rotatably mounted with the feeding box It is a vertical shaft I4carrying a feeding cone l5 upon which the bagasse is delivered from aplurality of feed spouts It on either side of' the feed cone so as tomore uniformly distribute the bagasse upon the rotating'feed cone. Thefeed cone may carry a plurality of radially disposed rabble arms forspreading the bagasse into the openings of a stationary distributingplate l8. Mounted immediately below and closely adjacent to the platel8-is an adjustable plate I! having openings corresponding to theopenings in. the distributing plate, the plate I! being adjustablearound the shaft I! so that it may-be adjusted with reference to theplate It and thus vary the size, of the openings in the distributingplate I l to variably control the feeding of bagasse into the drier. v Ii Below the distributing plate I. is a plurality of drying tiers 20similar to those of my copending application, each tier comprisingalternate reticulated sections 2| and open spaces 22, the reticulatedsections of each tier being immediately below an open space in the tierabove it 5 so that as the bagasse is brushed off the section 2| of onetier by a rotating rabble arm 23, it will be brushed into an adjacentopening 22 and fall directly upon a reticulated support 22 below. Thenumber and size of the tiers, as well as the number of rabble arms foreach tier will, of course, vary according to the capacity of the plantand the degree of dryness to be desired.

According to the present invention, the drying is effected by moving thewet bagasse for a sub- 15 stantial distance in a current of very hot airor flue gas, preferably at a temperature of about 800 to 1000 F. toextract a substantial amount of moisture from the material and thencom-- pleting the drying of the bagasse-by moving it in 2 acounter-current of hot air at a temperature of between 250. and 400 F.

The hot flue gases and heated air may be supplied from a suitablesource, as for example, a Dutch oven 25 having a cook's furnace 26adapted to burn a.quantity of bagasse which advantageously may be apercentage of the bagasse dried in the drier. The cook's furnace of theoven 25 may be supplied with a forced draft-in the usual manner andasecondary combustion chamber 21 as is usual. The products of combustionof the furnace are advantageously divided and may be variably controlledas by damper 21*, a major portion of the gas being passed through flue28 to an annular air inlet 29 surrounding the feed box I II and directedinwardly-to the'interior of the feed box, by means of radial openings ornozzles 20 so that the applicatiomof the hot flue gases to the wetbagasse will be as uniform as possible circumferentially of the drier.

The balance-of the products of combustion 3g; from the Dutch oven arepassed through'a heat exchanger 3] which may advantageously be of anysuitable design by means of which air, culated by fanJ-2 may be heatedto a suitable 45 degree, the flow of.flue gases through theflieatexchanger II, and hence the temperature of air heated thereby, beingcontrolled by valve 33.

The air heated by the heat exchanger" passes through conduit 34 to anannular hotair inlet 5o 35 surroundingthe drier casing 12 at its lowerend, the hot air being admitted to the interior of the casing II bymeans of openings or nozzles 36 so that the appllcationof heated airtothebagasewlllbeuniformcircumferentiauyu' pressure from the plunger 43.

of the drier. Obviously the temperature of the hot flue gases enteringthe feed box III may be variably controlled by suitable means, as forexample, a damper regulating the admission of air to the secondarycombustion chamber 21 of the oven 26.

A fan- 38 is preferably provided to draw off the dust and moisture ladenair and gases from the drier casing and preferably this fan is connectedto the casing intermediate the flue gas inlet at the upper end of thedrier and the hot air inlet and the lower end of the drier. Preferablythe exhaust fan 38 is connected to the drier by means of an annularoutlet or exhaust chamber 39, and the fan advantageously delivers thedust laden air and gases to a suitable dust collector which may be ofthe cyclone type. The fan 38 is of sufficient capacity as to produce anegative pressure with the casing I3.

It is important that the drying take place within an enclosed chamberand in the absence of air, except the hot air and gases which arecirculated through the drier, and hence it is advantageous to provide anair lock both at the feeding and discharge end of the. drier. This maybe satisfactorily accomplished by means of the star wheel mechanismdisclosed in my copending application, but in connection with thedischarge I find the more satisfactory air lock is obtained according tothe present invention.

Accordingly, the lower end of the casing l3 may comprise downwardly andinwardly inclined walls-forming a discharge cone 4|, the coneterminating at its lower end in a horizontal tube 42. The lower end ofthe shaft may be provided with a stirrer or scraper 43 to preventbridging of the dried bagasse in the cone, and to permit a normal flowof dried material to the tube 42. A plunger 44 reciprocated by anysuitable means, as for example, a crank 45 and connecting rod 46 ismounted within the tube to discharge the bagasse from the discharge cone4|, the number of strokes of the plunger 44 as well as the diameter ofthe tube 42 being proportioned and designed so as to progressivelydischarge bagasse in accordance with the capacity of the drier and therate of feeding material to the feed box II).

In order to provide an air lock against the admission of atmospheric airinto the drier at the discharge cone, the tube 42 preferably terminatesin reduced discharge tube 41 effective to retard the flow of driedbagasse except under The cooperating action of the plunger 43 and thereduced discharge tube efiect a compacting. of the bagasse fibers in thedischarge tube effective to seal the tube 45 against the entrance of airand also to deliver the dried bagasse in partially compressed batches,which are more advantageously baled in baling presses than when. thematerial is loose and flocculent;

The shaft I 4 advantageously extends longitudinally of the full heightof the drier and may be advantageously driven by suitable speedreduction gearing 48 at the upper end.

Advantages of my present invention over the method and apparatusdisclosed in my copending application Serial No. 738,112 are that a morecomplete dryingv of the bagasse may be effected in a shorter time andhence the capacity of the drier may be increased without seriousliability to fires occuring in the drier. By first subjecting the wetbagasse to the hot flue gases which may be as hot as 800 to 1000 F. topartially dry them, and -then finally drying the bagasse in a current ofair at from 250 to 400 F.,

' I am able to dry bagasse to a high degree of dryness (with a moisturecontent as low as 7%) in a relatively shorter time than was possiblewith the method disclosed .in my copending application. For example, thedrying may be completed according to the present invention, in 15minutes, and preferably the exhaust or discharge outlet 39 isso locatedthat bagasse is subjected to the hot flue gases for 60% of the dryingtime, and to the counter flow ofhot air for approximately of the dryingtime. This I find is an extremely efiicient drying method and enables meto reduce the number of drying tiers I .over my prior method.

I claim:

Apparatus for drying loose vegetable fibers such as bagasse, comprisinga closed vertical casing, a vertical shaft rotatably mounted in saidcasing, a conical distributor connected to the upper end of the shaft,means for introducing fibers into the casing and upon said distributor,a plurality of reticulated tiers spaced throughout the length of thecasing, means for progressively conveying the fiber material from onetier to the next lower tier, an auxiliary furnace, means for conveyinghot flue gasesof approximately 750 F. from said furnace and introducingthem into the top of said chamber in contact with the fibrous material,a heat exchanger heated by said furnace, means for circulating dryingair through said heat exchanger and induring the first operation ofdrying period, and

a current of cooler drying air moving in a counter direction to themovement of the fibrous material during the latter portion of the dryingperiod.

GASTON J. LIPSCOMIB.

